Motor vehicles are frequently stolen because the thief can circumvent the ignition switch, or the user forgets the key in the ignition switch. Some vehicles employ a so-called "kill switch" that interrupts the electrical connection between the ignition switch and the starter, however, this switch can often be circumvented by the thief who either hot wires the starter, or the owner either forgets to manipulate the "kill switch" or finds it too much of a nuisance and leaves it in its inoperative position. Such a system is basically an active system because it requires the user to actively take some measures to put the vehicle's electrical circuitry in an inoperative condition. If, as frequently happens, the user either forgets or does not desire to use the anti-theft system, the vehicle remains unprotected.
Still another problem is that some commercially available systems require the owner to maintain his door in a locked condition in order to set an alarm. As a result, the thief will break the window to gain access to the car.
My earlier U.S. Pat. No. 4,186,710, which was issued Feb. 5, 1980, disclosed a vehicle anti-theft system in which both terminals of the starter are grounded to the vehicle frame so that in the event that the thief hot wires the starter, the hot wire creates a short circuit and burns the thief.